Cannot Create Bootable USB key using 1.7.8 on 2017 iMac

continuing from my post here:

http://www.deploystudio.com/Forums/viewtopic.php?pid=29694#p29694

Cannot make a Bootable USB drive on a new 2017 iMac with DeployStudio 1.7.8 installed.Makes .nbi files fine, but either with new out the box USB drives or existing ( made with v.1.7.6) USB drives, it fails to create.